A valve is used to control the flow of a substance through a passage such as tubing or piping. (An example of such a valve is shown in FIG. 1.) The valve typically has a valve handle which is used to operate the valve. One type of valve lockout device fits onto the valve and holds the valve handle in a particular position, typically the closed position. The lockout device can be used, for example, to prevent the valve from being operated accidentally while components downstream from the valve are being serviced. This is particularly useful where the valve is controlling isolation of a dangerous substance. For example, in processing semiconductor substrates, poisonous, corrosive, and inert gases are normally used during processing, and exposure of human beings to such gases is hazardous. For safety, isolation of the dangerous substances is required, and locking of the valve in a closed position is required by good safety practices and industrial regulations.
There are problems with existing valve lockout devices. Often valves are lined up in a valve box with very little space between them, making it difficult for the lockout devices to fit. A valve lockout device may fit a particular valve model but not other valve models, especially where the different valve models are made by different manufacturers. Some valve lockout devices may be designed so that part of the lockout device is an integral part of the valve itself, or the lockout device requires some special structure associated with the valve, or the valve must be taken apart to install the lockout device, or part of the lockout device remains attached to the valve when the rest of the lockout device is removed. Other lockout devices have several pieces which are cumbersome or difficult to join in small spaces.